Abstract
Treatment of N-furoyltryptophan with polyphosphate ester in chloroform afforded 2-furoylamino-4-methy1cyc1opent[b]indol-3-one (VIII), but not 3, 4-dihydro-β-carboline derivatives (VII). The structure of VIII was confirmed from infrared, nuclear magnetic resonance and mass spectral data. Catalytic hydrogenation of VIII in acetic acid in the presence of platinum oxide as a catalyst gave a diastereoisomeric mixture of the tetrahydrofuran derivatives, whose spectral data supported the structure (IX), and the ring closure by way of route c was found to have occurred.
